Recently, a PC has one or more USB ports as a standard specification. The USB provides a function for connecting a device (an external apparatus) in the tree structure, a function for supporting two transmission speeds of 12 megabits per second and 1.5 megabits per second, a function for supporting PnP (Plug and Play), a function for supplying power to a connected device, and a function for supporting hot plug (which enables to connect and disconnect with a running PC).
A method for supplying power to a display device through a USB is disclosed in Japanese Patent Publication No. JP10-326128. In this method, the power is saved effectively by supplying power to a display device through a USB at a power-saving mode.
In general, a keyboard, a mouse and the like, which need to be supplied low-level power, are connected with the USB port having such functions. Also as the USB port supports the transmission speed of 12 megabits per second, a printer, a scanner and the like can be also connected.
On the other hand, as Internet and a mobile phone have been popularized, the mobile phone is usually used as a communication medium while being connected with the Internet.
Moreover, as the memory function and the display function of the mobile phone have been improved, the mobile phone is capable of recording data not only telephone numbers but also addresses, names and ringing melodies concerned with the telephone numbers in the memory and is capable of displaying the data.
Also, software for reading and editing the data recorded in the memory of the mobile phone and for recording the data in the memory of the mobile phone, by connecting the mobile phone with the PC, is sold.
Like the above, a variety of apparatuses are connected with the USB port of the PC, and the mobile phone is generally used while being connected to the PC. Also, as the opportunity to send and receive electronic mails via the Internet increases, the mobile phone is generally used while being connected to the PC.
In the conventional cable for connecting the mobile phone and the like with the PC, however, there are disadvantages in that the battery of the mobile phone needs to be recharged at the time of starting to use the mobile phone while connecting to the PC, because the batteries of the mobile phone and the like are charged by a special battery charger.